R8C5 can only be <6>
R4C2 is the only square in row 4 that can be <1>
R3C3 is the only square in row 3 that can be <1>
R6C8 is the only square in row 6 that can be <6>
R6C9 is the only square in row 6 that can be <2>
R6C1 is the only square in row 6 that can be <8>
R7C9 is the only square in row 7 that can be <1>
R8C4 is the only square in row 8 that can be <1>
R2C5 is the only square in column 5 that can be <7>
R5C6 is the only square in column 6 that can be <5>
R5C8 can only be <7>
R5C2 can only be <3>
R4C8 can only be <5>
R4C9 can only be <3>
R4C5 can only be <9>
R5C4 can only be <6>
R6C2 can only be <9>
R2C4 can only be <4>
R6C5 can only be <3>
R4C1 can only be <7>
R2C9 can only be <5>
R1C4 can only be <8>
R1C6 can only be <9>
R9C4 can only be <3>
R2C6 can only be <6>
R8C3 is the only square in row 8 that can be <7>
R8C9 is the only square in row 8 that can be <4>
R3C9 can only be <8>
R8C6 is the only square in row 8 that can be <8>
R9C6 can only be <2>
R9C2 can only be <6>
R3C1 is the only square in row 3 that can be <6>
R7C7 is the only square in row 7 that can be <6>
R9C7 is the only square in row 9 that can be <5>
Intersection of row 3 with block 3. The value <9> only appears in one or more of squares R3C7, R3C8 and R3C9 of row 3. These squares are the ones that intersect with block 3. Thus, the other (non-intersecting) squares of block 3 cannot contain this value.
R2C7 - removing <9> from <239> leaving <23>
Squares R2C1 and R2C7 in row 2 and R8C1 and R8C7 in row 8 form a Simple X-Wing pattern on possibility <2>. All other instances of this possibility in columns 1 and 7 can be removed.
R1C7 - removing <2> from <237> leaving <37>
R7C1 - removing <2> from <23> leaving <3>
The puzzle can be reduced to a Bivalue Universal Grave (BUG) pattern, by making this reduction:
R1C2=<27>
These are called the BUG possibilities. In a BUG pattern, in each row, column and block, each unsolved possibility appears exactly twice. Such a pattern either has 0 or 2 solutions, so it cannot be part of a valid Sudoku
When a puzzle contains a BUG, and only one square in the puzzle has more than 2 possibilities, the only way to kill the BUG is to remove both of the BUG possibilities from the square, thus solving it
R1C2 - removing <27> from <247> leaving <4>
R1C3 can only be <3>
R1C8 can only be <2>
R3C2 can only be <7>
R7C2 can only be <2>
R1C7 can only be <7>
R2C3 can only be <9>
R3C7 can only be <9>
R7C8 can only be <8>
R2C7 can only be <3>
R2C1 can only be <2>
R9C3 can only be <8>
R3C8 can only be <4>
R8C7 can only be <2>
R8C1 can only be <9>
R7C3 can only be <4>
R9C8 can only be <9>